“Climate change threatens all of us, but it is the world’s most vulnerable who are already paying for developed countries’ failure to act with their lives and livelihoods,” wrote the Nobel laureates in a June 17 letter to Obama and Kerry. “This will only become more tragic as impacts become worse and conflicts are exacerbated as precious natural resources, like water and food, become more and more scarce. Inaction will cost hundreds of millions of lives—and the death toll will only continue to rise.”

Indigenous leader Rigoberta Menchú Tum of Guatemala, who was awarded the peace prize in 1992, was among the signers. Besides Menchú, the letter was signed by Mairead Maguire and Betty Williams, both of Ireland, who won in 1976; Archbishop Desmond Tutu of South Africa, 1984; Adolfo Pérez Esquivel, 1980, Argentina; José Ramos Horta, East Timor, 1996; Jody Williams, United States, 1997; Shirin Ebadi, Iran, 2003; Tawakkol Karman, Yemen, 2011, and Leymah Gbowee, Liberia (2011).

This was the second time Nobel laureates had appealed to the President about Keystone XL. In September 2011, nine honorees signed a similar letter, including Menchú, Maguire, Williams, Tutu, Esquivel, Ramos Horta, Williams and Ebadi. His Holiness the Dalai Lama also signed the earlier letter. Last week's letter was dated the same day that the outgoing U.S. Ambassador to Canada, David Jacobson, told the Associated Press it is a “very important decision.”

Just a few days earlier, former Vice President Al Gore, a 2007 Nobel Peace Prize winner for his anti–climate change activism, had called Keystone XL “an atrocity” in an interview with the Guardian. He said Obama would do well to focus his energy instead on a comprehensive climate change plan.

"This whole project [Keystone XL] is an atrocity but it is even more important for him to regulate carbon dioxide emissions," Gore told the British newspaper, adding that curtailing carbon dioxide emissions from power plants would go far in counteracting global warming.

Gore's sentiments were in line with those expressed in the letter to Obama, though he was not among the signers. Contending that turning down Keystone XL would curtail or limit development in the oil sands of Alberta, Canada, the Nobel laureates, too, urged the Obama Administration to take a global lead on combating climate change and spearheading the movement away from fossil fuels. Many of the signees belong to the Nobel Women's Initiative, established in 2006 by six of the 15 women who have received the Nobel Peace Prize in the 110 years it has been awarded.

“Like millions of others, we were buoyed by words in the President’s second inaugural address: ‘We will respond to the threat of climate change, knowing that failure to do so would betray our children and future generations,’ ” the letter stated. “Mr. President and Secretary Kerry, this is an opportunity to begin to fulfill that promise. While there is no one policy or action that will avoid dangerous climate change, saying ‘no’ to the Keystone XL pipeline is a critical step in the right direction. Now is the time for unwavering leadership.”

These assertions about oil sands development directly contradicted the findings outlined in the State Department’s preliminary environmental assessment report, released in March, that said Keystone XL would produce negligible effects both on climate change and oil sands development. (Related: State Department Draft Environmental Report Says Keystone XL Effects on Both Climate Change and Oil Supply Would Be Minimal)

The Keystone XL pipeline would wend its way from Canada to the Gulf coast of the United States bringing up to 800,000 of viscous crude along 1,700 miles. It would cost about $7 billion to build. Though supporters say it would create jobs, the State Department report also said that the overall economic impact would be negligible. (Related: Exaggerated Consultation Claims, Factual Errors in State Department's Keystone XL Environment Report Rankle Natives)

The first industrial revolution burned-out 40% of the world's oxygen. The remaining 60 % will get a sped up exit from our atmosphere if the Alberta Tar Sands Project reaches full exploitation. Pipelines to Canada's west Coast and East Coast are planned, One through Kitamat and another into Vancuver's harbour, called the Kinder Morgan line. This will inevitably cause more pollution along the west coast. Not to mention the pipeline into Texas.